In Silverlight, using MVVM I define a base class for related ViewModels and a list of possible values for a property defined in several child classes:
namespace MyNameSpace
{
public class MyViewModelBase
{
public static List<MyPropertyClass> MyPropertyValueList
{
get
{
if (myPropertyValueList == null)
{
// fill the list
}
return myPropertyValueList;
}
}
private static List<MyPropertyClass> myPropertyValueList = null;
}
}
Now I define my ViewModel:
namespace MyNameSpace.MyChild
{
public class MyViewModelChild
{
public MyPropertyClass MyProperty
{
get
{
return myProperty;
}
set
{
myProperty= value;
RaisePropertyChanged("MyProperty");
}
}
...
}
}
And I bind to my ViewModel
<controls:ChildWindow
x:Class="MyNameSpace.MyChild.MyChildEditor">
<ListBox ItemsSource="{Binding Path=MyPropertyValueList, Mode=OneTime}" SelectedValue="{Binding Path=MyProperty, Mode=TwoWay}"/>
Then the binding fails for MyPropertyValueList.
But if the MyPropertyValueList is defined in the child class it works. What am I doing wrong ?
You defined MyPropertyValueList as static property. It's not allowed in Silverlight.
Related
I am developing an application in WPF in which I want to populate a ListBox on selecting a node of a TreeView. I have populated the TreeView using MVVM pattern. It actually contains the the drives (C:\, D:...) and their corresponding sub-folders. The sub-folders are the nodes. On selecting these nodes the respective files should be shown in the ListBox. I know the C# code to get all the files in a folders, I have also implemented the same. However, I am not getting any clue to map them, so that on selecting the nodes the files in them should get reflected in the ListBox.
Can any please help me in this regard? The application is being developed in MVVM pattern and I need in the same pattern itself.
First add a Files collection class to your folder class (used in the tree view)
public class FolderItem
{
// other class code
private ObservableCollection<File> _Files = null;
public ObservableCollection<File> Files
{
get
{
if (_Files == null) _Files = GetFiles();
return _Files;
}
set
{
_Files = value;
}
}
}
Then bind the listbox to the selected treeview item.
<ListBox ItemsSource="{Binding ElementName=myTreeView, Path=SelectedItem.Files}"/>
You might have quite a number of files and folders so I think I would be inclined to lazy load as much as I could.
That means the viewmodel doesn't need to go iterate through the entire hard drive initially but you need some way of acting when selecteditem changes.
You can't bind selecteditem to a viewmodel because it's read only.
I would therefore use a behaviour like:
Data binding to SelectedItem in a WPF Treeview
Bind a SelectedFolder using that.
In the setter of SelectedFolder go get the list of folders and files for that folder and fill the two collections. One is the child collection of that selecteditem - for it's folders.
The other is an observableCollection for the files to see in the listbox.
Make that a propfull and implement inotifyproprtychanged so when I set it to a new collection it notifies the ui.
Bind that collection to the itemssource of the listbox.
Basicly The MVVM pattern uses three Layers :
The Model : Basicly it contains the Model classes and the business logic to get and manipulate Data information.
The ViewModel : It acts as an intermediate layer between the Model and the Views, it is attached to the different views.
The views : The différent views of the app.
Here an example how to fill a Window with list of Drives and Files.
Class BindableBaseViewModel
namespace TalkRepeater.ViewModel
{
public class BindableBaseViewModel : DependencyObject,INotifyPropertyChanged
{
protected virtual void SetProperty<T>(ref T member, T val,[CallerMemberName] string propertyName = null)
{
if (object.Equals(member, val)) return;
member = val;
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
public event PropertyChangedEventHandler PropertyChanged = delegate { };
}
}
Class ViewModel
public class FoldersControlViewModel : BindableBaseViewModel
{
private ObservableCollection<Folders> _listFolders;
private ObservableCollection<Folders> _listFiles;
public FoldersControlViewModel()
{
FoldersBusinessObject vbo =new FoldersBusinessObject()
vbo.FillFolders();
ListFolders = FileBusinessObject.ListFolders;
}
public ObservableCollection<Folders> ListFolders
{
get
{
return _listFolders;
}
set
{
_listFolders = value;
OnPropertyChanged("ListFolders");
}
}
public ObservableCollection<Folders> ListFiles
{
get
{
return _listFiles;
}
set
{
_listFiles = value;
OnPropertyChanged("ListFiles");
}
}
Public void FillListFiles()
{
/*ListFiles= Cod to fill ListFiles*/
}
}
Class BusinessObject
public class FoldersBusinessObject
{
private ObservableCollection<Folders> _ListFolders;
public void FillFolders()
{
/* ListFolders= Code To fill the collection ListFolders */
}
public ObservableCollection<Folders> ListFolders
{
get
{
return _ListFolders;
}
set
{
_ListFolders = value;
}
}
}
Foldersview
<Window x:Class="Foldersview"
xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x = "http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc = "http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d = "http://schemas.microsoft.com/expression/blend/2008"
d:DesignHeight = "300" Width="1007" Height="606">
<Grid Margin="10" >
<Canvas x:Name="canvasFolders" Margin="-10,0,912,10">
<TreeView x:Name="TreevFolders" ItemsSource="{Binding Path=ListFolders, Mode=TwoWay}" Canvas.Top="5" Canvas.Left="17" Width="142" Height="561"
SelectedItemChanged="TreevFolders_SelectedItemChanged" >
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Path=ListFolders}">
<TextBlock Text="{Binding Path=FileName}">
</TextBlock>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
</Canvas>
<Canvas Margin="159,10,0,10">
<Listview x:Name="Listview1" ItemsSource="{Binding ListFiles, Mode=TwoWay}" >
</Listview>
</Canvas>
</Grid>
</Window>
Class Foldersview Code Behind
public partial class Foldersview : Window
{
private void TreevFolders_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
FoldersControlViewModel vmd = (FoldersControlViewModel)this.DataContext;
vmd.FillListFiles ();
}
}
Class Mainwindow
public class MainWindowViewModel : BindableBase
{
private FoldersControlViewModel FoldersviewModel;
public MainWindowViewModel()
{
FoldersviewModel = new FoldersControlViewModel();
Foldersview=new Foldersview();
Foldersview.Datacontext=FoldersviewModel;
}
}
Cordialy
I have a simple listbox in a template file as follows:
<local:ProcessVisualization x:Key="ProcessVisualization"/>
<ListBox Grid.Column="1"
Grid.Row="1"
ItemsSource="{Binding Source={StaticResource ResourceKey=ProcessVisualization}, Path=Instance.TestListItems}"
SelectedItem="{Binding Source={StaticResource ResourceKey=ProcessVisualization}, Path=Instance.SelectedTestListItem, Mode=TwoWay}">
</ListBox>
Then in my ProcessVisualization class I have the following:
private ObservableCollection<string> _testListItems;
private string _selectedTestListItem;
private static readonly ProcessVisualization _processVisualization = new ProcessVisualization();
public ObservableCollection<string> TestListItems
{
get { return _testListItems; }
set
{
_testListItems = value;
NotifyPropertyChanged("TestListItems");
}
}
public string SelectedTestListItem
{
get { return _selectedTestListItem; }
set
{
_selectedTestListItem = value;
NotifyPropertyChanged("SelectedTestListItem");
}
}
public static ProcessVisualization Instance
{
get { return _processVisualization; }
}
When I run methods that assign lists of strings to TestListItems, they show up properly in my listbox, and I can set SelectedTestListItem from code without issue. But if a user tries to pick from the listbox, it doesn't seem to get back to updating my property on the ProcessVisualization class. Anyone know what I did wrong?
Say for example I have the following type:
public class Site
{
public string Name { get; set; }
public int SiteId { get; set; }
public bool IsLocal { get; set; }
}
The above type can be assigned to be held in a Propety in a ViewModel like so assuming a corresponding backing field has been created but omitted here ofc:
public Site SelectedSite
{
get { return _selectedSite; }
set
{
_selectedSite = value;
// raise property changed etc
}
}
In my xaml a straight forward binding would be:
<TextBlock x:Name="StatusMessageTextBlock"
Width="Auto"
Height="Auto"
Style="{StaticResource StatusMessageboxTextStyle}"
Text="{Binding MessageToDisplay,
Mode=OneWay,
UpdateSourceTrigger=PropertyChanged}" />
Can you extend a binding by using the dot notation syntax? e.g:
<TextBlock x:Name="StatusMessageTextBlock"
Width="Auto"
Height="Auto"
Style="{StaticResource StatusMessageboxTextStyle}"
**Text="{Binding SelectedSite.Name,**
Mode=OneWay,
UpdateSourceTrigger=PropertyChanged}" />
Seems like a an interesting feature but my gut instinct is a no as my DC is being assigned at RunTime so at DesignTime or CompileTime, I can't see any clues that could make this feature work or not?
Correct me if have misunderstood what a complex object is, I have simplified mine down for the sake of this question.
Of course this is possible. However, WPF needs to know when any property along the path has changed. To that end, you need to implement INotifyPropertyChanged (or other supported mechanisms). In your example, both Site and the VM containing SelectedSite should implement change notification).
Here's how you could implement the functionality you specified in your question:
// simple DTO
public class Site
{
public string Name { get; set; }
public int SiteId { get; set; }
public bool IsLocal { get; set; }
}
// base class for view models
public abstract class ViewModel
{
// see http://kentb.blogspot.co.uk/2009/04/mvvm-infrastructure-viewmodel.html for an example
}
public class SiteViewModel : ViewModel
{
private readonly Site site;
public SiteViewModel(Site site)
{
this.site = site;
}
// this is what your view binds to
public string Name
{
get { return this.site.Name; }
set
{
if (this.site.Name != value)
{
this.site.Name = value;
this.OnPropertyChanged(() => this.Name);
}
}
}
// other properties
}
public class SitesViewModel : ViewModel
{
private readonly ICollection<SiteViewModel> sites;
private SiteViewModel selectedSite;
public SitesViewModel()
{
this.sites = ...;
}
public ICollection<SiteViewModel> Sites
{
get { return this.sites; }
}
public SiteViewModel SelectedSite
{
get { return this.selectedSite; }
set
{
if (this.selectedSite != value)
{
this.selectedSite = value;
this.OnPropertyChanged(() => this.SelectedSite);
}
}
}
}
And your view might look something like this (assuming a DataContext of type SitesViewModel):
<ListBox ItemsSource="{Binding Sites}" SelectedItem="{Binding SelectedSite}"/>
Below is what worked for me:
public Site SelectedSite
{
get { return _selectedSite; }
set
{
_selectedSite = value;
RaisePropertyChanged("SelectedSite");
}
}
In my xaml I was able to do:
<TextBox Name="tbSiteName"
Width="250"
Height="30"
Margin="0"
HorizontalAlignment="Left"
VerticalAlignment="Top"
IsReadOnly="True"
Style="{StaticResource MainTextBoxStyle}"
Text="{Binding SelectedSite.Name,
Mode=OneWay,
UpdateSourceTrigger=PropertyChanged}" />
This allows you to access data members off the Site Type without having to create individual properties that wrap each data member on the Site Type. Then individual controls can bind to each property declared in the VM. In a one to one fashion, this aproach can become rather verbose. The binding extension attached to the Text property of the TextBox control shown above, shows that we are not binding to a simple straight forward property but actually to a custom type. Potentially removing the need to create more public properties.
I want to bind a TextBox in the window to a property contained within a class that is a variable of the viewmodel and ensure that INotifyPropertyChanged's PropertyChanged event propagates from the class to the parent.
Let me illustrate with an example:
(Window's DataContext is set to an instance of ViewModel)
public class ViewModel {
private OtherClass classInstance = new OtherClass();
public int Attribute {
get { return classInstance.Attribute; }
}
}
public class OtherClass : INotifyPropertyChanged {
private int _attribute;
public int Attribute {
get { return _attribute; }
set {
_attribute = value;
PropertyChanged("Attribute");
}
}
...
}
The problem in this example is that, when Attribute changes, the bound Textbox does not update the binding since I assume it's listening to the ViewModel's PropertyChanged event and not that of the instance of OtherClass.
Any ideas on how to remedy this situation? I was thinking about chaining OtherClass's INotifyPropertyChanged to that of its parent, but there has to be a better way.
Why not bind directly to the class property instead of using a proxy?
public class ViewModel {
private OtherClass classInstance = new OtherClass();
public OtherClass MyOtherClass {
get { return classInstance; }
}
}
Then in your binding you can simply reference the property via the SubClass
{Binding MyOtherClass.Attribute}
A drop dead simple example, but it works!
The Code Behind:
public partial class MainWindow : Window {
private readonly SomeClass _someClass = new SomeClass();
public MainWindow() {
InitializeComponent();
DataContext = _someClass;
}
}
public class SomeClass: INotifyPropertyChanged {
private readonly SomeSubClass _mySubClass = new SomeSubClass();
public SomeSubClass MySubClass {
get { return _mySubClass; }
}
private String _name;
public String Name {
get { return _name; }
set {
_name = value;
OnPropertyChanged("Name");
}
}
//Property Change Stuff
}
public class SomeSubClass : INotifyPropertyChanged {
private String _name;
public String Name {
get {
return _name;
}
set {
_name = value;
OnPropertyChanged("Name");
}
}
//Property Change Stuff
}
The XAML:
<Window x:Class="JWC.Examples.WPF.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow">
<StackPanel>
<Label Content="Name" VerticalAlignment="Top" />
<TextBox Text="{Binding Name}" />
<Label Content="SubClass.Name" />
<TextBox Text="{Binding MySubClass.Name}" />
<Label Content="Bound to Name" />
<TextBlock Text="{Binding Name}" />
<Label Content="Bound to MySubClass.Name" />
<TextBlock Text="{Binding MySubClass.Name}" />
</StackPanel>
</Window>
You will need to do something like this:
public class ViewModel {
public ViewModel() {
classInstance = new OtherClass();
classInstance.PropertyChanged += HandleAttributeChanged;
}
private void HandleAttributeChanged(object Sender, NotifyPropertyChangedEventArgs args) {
PropertyChanged("Attribute");
}
}
I don't show it here, but you should also implement IDisposable and unsubscribe from the PropertyChanged event on your child, otherwise you will leak memory.
Alternatively you can expose the classInstance as a public property and set your binding to: ViewModel.classInstance. Note this needs to be a property and not the field itself.
I think the parent class should subscribe to the child propertyCahnged event..something like:
public class ViewModel
{
private OtherClass classInstance = new OtherClass();
public ViewModel()
{
classInstance.PropertyChanged += NotifyChildAttributeChanged;
}
public int Attribute
{
get { return classInstance.Attribute; }
}
}
NotifyChildAttributeChanged is basically a method that listens only to the "Attribute" property and fires a PropertyChanged notification of its own..
Of course our parent class must implement INotifyPropertyChanged as well as will all ViewModels (preferably) and your DataContext will detect the change.
To get around this you need to implement INotifyPropertyChanged on your view model as well. Just add the interface and the event and the rest will take care of itself - no need to chain the events / calls together.
Check out this for using reflection to get the property as well.
http://tsells.wordpress.com/2011/02/08/using-reflection-with-wpf-and-the-inotifypropertychanged-interface/
I have an ObservableCollection of "Layouts" and a "SelectedLocation" DependencyProperty on a Window. The SelectedLocation has a property called "Layout", which is an object containing fields like "Name" etc. I'm trying to bind a combobox to the SelectedLayout but it's not working.
The following does not work, I've tried binding to SelectedItem instead to no avail. I believe it may be something to do with the fact that I'm binding to a subProperty of the SelectedLocation DependencyProperty (though this does implement INotifyPropertyChanged.
<ComboBox Grid.Row="2" Grid.Column="0" x:Name="cboLayout" ItemsSource="{Binding Layouts,ElementName=root}" SelectedValue="{Binding SelectedLocation.Layout.LayoutID,ElementName=root}" DisplayMemberPath="{Binding Name}" SelectedValuePath="LayoutID" />
However, the following works (Also bound to the "SelectedLocation" DP:
<TextBox Grid.Row="4" Grid.Column="1" x:Name="txtName" Text="{Binding SelectedLocation.Name,ElementName=root,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" />
What type property Layouts has? I suppose something like this this: IEnumerable<Layout>.
But you bind selected value to Layout.LayoutID. So you got situation, when combo box contains Layout objects, and you try to select it by Int identifier. Of course binding engine can't find any Int there.
I have no idea about details of your code, so one thing I could propose: try to reduce your binding expression: SelectedItem="{Binding SelectedLocation.Layout,ElementName=root}.
If no success, provide more code to help me understand what's going on.
====UPDATE====
As I've said, you are obviously doing something wrong. But I am not paranormalist and couldn't guess the reason of your fail (without your code). If you don't want to share your code, I decided to provide simple example in order to demonstrate that everything works. Have a look at code shown below and tell me what is different in your application.
Class Layout which exposes property LayoutId:
public class Layout
{
public Layout(string id)
{
this.LayoutId = id;
}
public string LayoutId
{
get;
private set;
}
public override string ToString()
{
return string.Format("layout #{0}", this.LayoutId);
}
}
Class SelectionLocation which has nested property Layout:
public class SelectedLocation : INotifyPropertyChanged
{
private Layout _layout;
public Layout Layout
{
get
{
return this._layout;
}
set
{
this._layout = value;
this.OnPropertyChanged("Layout");
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string name)
{
var safeEvent = this.PropertyChanged;
if (safeEvent != null)
{
safeEvent(this, new PropertyChangedEventArgs(name));
}
}
}
And Window class with dependency properties (actually, in my example StartupView is UserControl, but it doesn't matter):
public partial class StartupView : UserControl
{
public StartupView()
{
InitializeComponent();
this.Layouts = new Layout[] { new Layout("AAA"), new Layout("BBB"), new Layout("CCC") };
this.SelectedLocation = new SelectedLocation();
this.SelectedLocation.Layout = this.Layouts.ElementAt(1);
}
public IEnumerable<Layout> Layouts
{
get
{
return (IEnumerable<Layout>)this.GetValue(StartupView.LayoutsProperty);
}
set
{
this.SetValue(StartupView.LayoutsProperty, value);
}
}
public static readonly DependencyProperty LayoutsProperty =
DependencyProperty.Register("Layouts",
typeof(IEnumerable<Layout>),
typeof(StartupView),
new FrameworkPropertyMetadata(null));
public SelectedLocation SelectedLocation
{
get
{
return (SelectedLocation)this.GetValue(StartupView.SelectedLocationProperty);
}
set
{
this.SetValue(StartupView.SelectedLocationProperty, value);
}
}
public static readonly DependencyProperty SelectedLocationProperty =
DependencyProperty.Register("SelectedLocation",
typeof(SelectedLocation),
typeof(StartupView),
new FrameworkPropertyMetadata(null));
}
XAML of StartupView:
<UserControl x:Class="Test.StartupView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:self="clr-namespace:HandyCopy"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Name="Root">
<WrapPanel>
<ComboBox ItemsSource="{Binding Path=Layouts,ElementName=Root}"
SelectedItem="{Binding Path=SelectedLocation.Layout, ElementName=Root}"/>
</WrapPanel>
</UserControl>